CD8+ CTLs play a vital role in controlling viral infection. CD8+ cells have the ability to recognize virally infected cells that present peptide epitopes derived from viral proteins on MHC class I molecules on their surfaces. In the development of vaccines for HIV-I, it is necessary to focus on the induction of a CTL response. There are numerous factors influencing the induction of antigen-specific CTL responses. This project focuses on the efficiency with which the foreign Ag is processed. HIV-I gag is a highly conserved gene among various HIV-1 isolates and therefore is an attractive candidate for a CTL-based vaccine. The goal of this project is to generate rapidly degrading forms of HIV-1 gag and the evaluate their ability to enhance the induction of gag specific CTLs in vivo. Soluble multivalent MHC molecules and T cell receptors (TCRs) will be used to evaluate the novel vaccine strategies for the induction of antigen-specific CTL. This proposal will focus primarily on the following specific aims: 1) Generation of degradation targeted gag constructs. 2) Generation of soluble gag-specific TCRs. 3) Utilization of soluble divalent TCRs to measure the number of Ag/MHC complexes generated on the surfaces of cells expressing gag Ags targeted to the class I pathway. 4) Use of soluble, peptide-loaded MHC class I dimers and conventional CTL methods in order to evaluate the ability of novel vaccine strategies to induce HIV-1 gag specific CTL responses.